The Franklin 8 series of 8-cylinder air-cooled horizontally opposed aircraft engines produced in the 1940s and 1950s, (US military designation O-540 was applied to the 8ACG-538, 8ACSA-538 and 8ACGSA-538).
Data from:
8AC-398
200 hp (149 kW) @ 2,600 rpm.
8ACG-398
235 hp (175 kW) @ 3,500 rpm. The 8ACG-398 was unusual in using a reduction gearing for take-off and direct drive for cruising.
8ACG-538
300 hp (224 kW) @ 3,200 rpm geared to 0.632 (XO-540-1)
8ACGSA-538
300 hp (224 kW) @ 3,200 rpm supercharged and geared to 0.632 (XO-540-3 and O-540-5)
8ACSA-538
300 hp (224 kW) supercharged (XO-540-7), powered the Northrop N-9MB.
O-540
Military designation for the 8ACG-538, 8ACSA-538 and 8ACGSA-538 engines
Data from:
Northrop N-9MB
